NASHUA – A Milford man involved in a fatal car crash on Christmas Eve that left a Brookline mother dead has been indicted on negligent homicide charges.

Greg Cullen, 31, of 166 Badger Hill Road, Milford, was indicted by a Hillsborough County Superior Court grand jury last month and charged with killing 30-year-old Brookline mother Katie Hamilton in front of the Brookline Safety Complex the day before Christmas, according to court documents.

Cullen was distracted by his cellphone and rear ended Hamilton’s car, pushing it into oncoming traffic, according to the indictment.

The indictment, part of the 107 charges handed down by the grand jury last month, are not a finding of guilt. They are the grand jury’s determination that prosecutors have enough evidence to move the case forward at the superior court level.

State police investigated the Dec. 24 crash in Brookline that killed Hamilton, whose father, Steve Whitcomb, is a longtime firefighter in the town and was among the rescuers who responded to the scene.

Cullen was driving a 2009 Toyota pickup truck on Route 13 when he hit Hamilton’s vehicle from behind. Hamilton’s SUV was pushed into oncoming traffic and was hit by a Ford F250 truck. She was pronounced dead at the scene, police said.

Brookline Police Chief William Quigley said after the crash that police had ruled out speed or impairment leading to the crash but were investigating whether Cullen was using his phone or was otherwise distracted.

Hamilton, a mother of three young girls, lived with her husband, Liam, on Bond Street and was a regular presence around the fire department.

The felony negligent homicide charge is punishable by up to 15 years in prison, according to court documents.

Joseph G. Cote can be reached at 594-6415 or jcote@nashuatelegraph.com. Also, follow Cote on Twitter (@Telegraph_JoeC).